1. Field of the Invention
The present invention relates to the use of coherent energy pulses as from high power pulsed lasers in the shock processing of solid materials, and more particularly to a device and method for generating a particularly formed laser beam profile for use in the process. The invention is especially used for enhancing on creating desired physical properties such as hardness, strength, and fatigue strength in solid materials.
2. Description of the Related Art
Known methods for the shock processing of solid materials, particularly known methods for the laser shock processing or peening of solid materials, typically use coherent energy from a laser beam oriented normal to a workpiece. The cross sectional shape of the laser beam may be circular for efficient laser beam creation, or for slab type laser rods, it may be rectangular.
Such circular cross sectional laser beams create circular laser peened spots on a workpiece surface when oriented normal thereto. As previously known in the art, to adequately laser shock the desired area in the workpiece, such geometry, i.e., circular, of the laser spot necessitated an overlap of adjacent laser shocked spots on the workpiece to sufficiently create a residual compressive field within the workpiece. Such overlap of the peened spots, reduces the speed of the process.
Lenses utilized within high powered laser systems have historically used only refractive lenses. Such lenses utilize a material such as glass or plastic having varying thicknesses to bend or refract the laser energy.
What is needed in the art, is the ability to change the circular cross section of the high power laser beam to that of an alternate shape, such that a majority of the laser energy created may be applied to the workpiece without substantial loss. Further, needed in the art, is an energy efficient method to alter a cross sectional shape of the incoming laser beam to permit efficient processing of the workpiece without necessitating overlap of the laser peened spots.
Also needed is a technique to provide more uniform energy distribution independent of spot shape.